Automatic transmissions, which make available different gears, are used in the construction of vehicles. The gears—abbreviated by P, R, N and D (P=Park, R=Reverse, N=Neutral, D=Drive) can be selected by the driver with a selector lever or a button. In modern vehicles, the gear selected by the driver is scanned by means of a corresponding electronic unit and electronically transmitted to the transmission electronic unit, which adjusts the transmission correspondingly. The previously common mechanical connection between the transmission and the manual gear input unit (selector lever and/or button) is now eliminated. This concept is generally called “shift-by-wire shifting.”
Shift-by-wire shifting has the basic problem that in case of emergency running of the transmission or failure of the electronic unit of the motor vehicle (failure of the transmission control device, failure of the shifting electronic unit, line break, failure of the power supply, etc.), the transmission is no longer able to carry out the driver's commands and the transmission is no longer able to be configured.
An optical, acoustic or haptic (tactile) feedback to the driver is known in such a situation from EP 1 062 439 B1. A haptic feedback is represented, for example, by an increase or reduction in the actuating force. Such haptic feedback, but also optical and acoustic feedbacks are not always reliably recognized by the driver, and they are even ignored in the worst case.
The blocking or fixing of the corresponding actuating element is a feedback that is guaranteed not to be able to be overlooked. As a result, the driver will immediately recognize that the desired setting of the transmission cannot be carried out or implemented.
Such a blocking of a single actuating element for conventional shifting mechanisms (cable or bar connection with the transmission) is known. The gears PARK and NEUTRAL are blocked under certain conditions especially in conventional automatic shifting mechanisms.
It is possible in shift-by-wire shifting mechanisms to split the selection of the different gears (P, R, N, D) between two or more actuating elements (for example, selector lever and button) or to incorporate additional actuating elements, which are not used to operate the transmission but have other functions, in the manual gear input unit.